U.S. Pat. No. 1,731,147 of Moyer et al and U.S. Pat. No. 3,015,529 of Hardcastle show built-up plungers constructed as a cylinder and heads on either end of the cylinder in Moyer and, similarily, a replaceable wear sleeve combined with a combination header and stud in Hardcastle. Moyer shows a unit held together by tension but which can also be in compression. Hardcastle shows the use of a tapered header. In neither case is the outer sleeve or cylinder intended as a significant load bearing member. U.S. Pat. No. 3,315,570 of Brewer et al shows one apparatus for relieving pressure at certain end positions of a power steering system in order to prevent excessive overloading or wear of steerage linkage. The pressure is automatically relieved once those end positions are reached.